In the gas stations, various methods are employed to measure the level of oil inside the underground fuel tanks. Such methods may be carried out manually by dipping the level measurement sticks in the tank, as well as automatically with the help of the electronic measurement sensors placed into the tank.
In all the said methods, the calculation is made for the amount of liters that the level measured in millimeters corresponds to. Said calculation is made using the calibration chart previously prepared for the fuel tank. The calibration chart shows the height of the fuel inside the tank and the volume value corresponding to the same. The height of the fuel inside the tank is calculated by means of the aforesaid methods and it is proportioned with respect to the tank volume, in order to determine the fuel amount (volume).
In order to perform this calculation accurately, the calibration chart (mm/It) of the fuel tank must be correct. Otherwise, the measured millimeter value will not yield the correct value in liters.
The calibration charts for the fuel tanks are generally drawn up during the production thereof. However, the chart is suitable for the ideal conditions and when the tank is placed underground, it deviates from said ideal conditions and the calibration chart of the tank becomes erroneous.
In this case, it is necessary to carry out the tank calibration again, in order to obtain an accurate result when the level measurement system is installed in the tank or when a manual measurement is performed. This is a difficult and costly work.
In order to carry out the calibration, the fuel inside the tank is emptied and millimeter measurement is made by stage wise filling of the fuel. For this system, the equipment such as one or two fuel tankers and the fuel transfer pump are used in the station and it may take hours to complete the calibration for one tank.
During said period of time, the operation of the station must be ceased in a stage wise manner and no sale must be conducted. Manual calibration is labor intensive and costly, in addition to its hindering the overall functioning of the station.
Another calibration method is carried out in an automatic manner by means of the calibration software and automation systems in the systems having the tank automation system and the pump automation system. With the automatic calibration initiated after the tanks are completely filled, the system compares the mm value it receives from the tank automation to the amount of fuel sold at the pumps, to prepare the calibration chart for the tank.
In order for this system to function accurately, it is necessary to wait for the tanks to become completely empty and there must no intervention in the meantime; also, in order to form a correct and complete chart, one needs to wait for the tank to be filled and emptied for several times.
In such automation systems, it is necessary to completely fill several times the expensive tanks with an average capacity of 20.000 lt. This situation leads to a high cost and a long duration of time. Also, as the durations become very long in the stations with a low rate of sale, difficulties are encountered in obtaining the correct results.
Today, in the PCT document no. WO2007078221 titled “the calibration method and apparatus for the determination of the amount of liquid inside the tank”, the invention disclosed relates to measuring and calibrating the fuel level inside a fuel tank by means of a fuel sensor. In said application, the amount of fuel inside the tank is measured according to the calibration value that corresponds to said fuel level.
However, when said tank is placed in an area that is not smooth according to this practice, said fuel levels appear with a value below or above the actual one with a certain inclination and the desired actual amount of fuel may not be reached.
Similarly, the EPC application no. EP1603826 titled “the measurement system for the underground liquid fuel tanks in the gas stations” relates to the system, which measures the amount of the fuel withdrawn from the liquid fuel tanks located underground of the gas stations. Here the measurement procedure is carried out by means of the turbine pump dipped into the tank. Amount of the fuel drawn by the gas pump is measured, and thus the amount of the remaining fuel may be calculated.
Unfortunately, it is also necessary in this practice to wait until the complete emptying of the tanks and there must no intervention meanwhile, in order for the system to function accurately.
Further according to the state of the art, in the patent document no. US2003230141 titled “optical fuel level sensor”, the variation in the fuel level is determined by means of an electronic level detection sensor.
Also in said practice, difficulties are encountered in eliminating the aforesaid disadvantages.
Due to the aforementioned disadvantages, the effort has been made in search of an innovation in the calibration method used to measure the fuel amount in the liquid fuel tanks.